1. Field of the Invention
The present invention relates to a device, a system and a method for three-dimensional scanning, more particularly for three-dimensional, or 3D, detection of physical objects of any geometry.
2. Present State of the Art
It is known that many measuring instruments exist which can copy, or replicate, the three-dimensional outline of a real object having a complex shape. These instruments are called “3D scanners” and are employed for industrial design, quality control, biomedical and other applications where digital copies of real objects are needed. Such systems may require the use of different technologies, each having specific limits, advantages and costs. According to a well-known and established classification, they are divided into two macrofamilies: “contact” systems and “contactless” systems.
“Contact” 3D scanning systems probe the external surface of the object by physical contact. The structure of these systems may include a rigid-arm transport system allowing the scanning head to move along the axes of the coordinates, e.g., Cartesian ones, or, more commonly, may include articulated arms fitted with joint-mounted displacement sensors which can detect the movements of a measuring head (also called “feeler”).
However, such “contact” systems with rigid or articulated arms are very bulky and difficult to move. As a matter of fact, they are totally inadequate for 3D scanning, or detection, of objects that cannot be moved from their original location, e.g., archeological finds.
As far as “contactless” systems are concerned, they employ optical systems making use of a light source (laser, light pattern and the like), and represent the most widespread solution currently available on the market. Among these, so-called “hand-held” scanners are now becoming more and more popular on the market, which use measuring-head tracking stations or place reference markers on the object itself or in the surrounding environment. These expedients are normally resorted to because the object cannot be wholly scanned by means of just one measurement, and multiple measuring steps have to be carried out. In order to ensure consistency of the results obtained by means of the various measurements, it is necessary to use common reference elements, e.g., markers, for all measurements, so as to define a univocal reference system.
However, these latter “contactless” systems using references, or markers, require post-processing operations for merging all the single measurements taken, i.e., an operator aligning and joining the single measurements. Moreover, the accuracy of the measurements is strictly dependent on the positions and quantity of the markers placed on the object. This factor introduces measurement errors that propagate into the final result, i.e., the full processing of the 3D model of the object under examination.